Rath-Amp Retro 80 repair - crackling sound, overdrive channel broken

[juho-eric]

Hi everyone,

First off, if anyone has a Rath-Amp Retro 80 service manual (or any Rath-Amp service manual), I would be more than glad to have a copy of it!

My friend's Rath-Amp Retro 80 is quite broken and I'm starting to fix it. There's several problems:

1. It gives a crackling sound all the time and sounds VERY broken...

2. Overdrive channel doesn't go on. When the overdrive button is pressed, nothing happens - the clean channel stays on and the ovedrive LED doesn't light up. My first quess was the switch itself, but it works fine according to my ohmmeter. Now I'm quessing that the relay on the PCB might be broken and causing this...

Or maybe the footpedal jack is causing this? I'm quessing the foot pedal controls the overdrive also. I don't have a manual so I don't really know

3. The MIDDLE and TREBLE pots crackle a lot on the clean channel. I'm not sure of the OD channel as it doesn't work. I'm planning to start here since I don't know yet the cause of the other problems. Maybe a REALLY broken EQ pot might cause the crackling problem #1...?

I would really appreciate some comments, thanks already!

[juho-eric]

I think I just fixed problem #2.
One metal part of the foot pedal jack was bent, so the normally-open switch was always open.
So the nonexistent foot pedal overrided the manual overdrive button.
I bent the metal part a bit and now it gives contact.

Testing if it works in a bit.

[juho-eric]

Shit, the connector between PSU/power amp board and the main board dropped off.
The connector is really shitty, made of IC sockets!
This caused the amp to burn it's fuse.
This is the second time I burn a fuse because of that connector.

Now I need to go buy a new fuse before I can test it again.

Hopefully nothing else got burned...

[juho-eric]

OK, put a new fuse in and now the overdrive channel works!
The cause for distortion channel not working was just the bent metal part on the foot pedal jack.

Still, the crackling sound is there. It's there on both the distortion and clean channels.
I have yet to try the LINE OUT to check if it's there too.

So probably the crackling is not caused by the bad pots on the clean channel.
Although I found out that the MIDDLE pot of the overdrive channel is also quite broken.
My first idea was that maybe the EQ is unstable due to the broken pots...

Now I'm thinking the cause for the crackling could be:
- Main power amp - hopefully not this
- Master volume circuit maybe?
- Power supply

[Enzo]

If you have broken parts, replace them. I can;t say it is your situation, but cracked controls can cause noise for sure.

[juho-eric]

If you have broken parts, replace them. I can;t say it is your situation, but cracked controls can cause noise for sure.

Yeah, definitely going to replace the 3 pots first.